Drawing-press.



No. 760,921. PATENTED MAY 24,1904.

J..J. RIGBY. DRAWING PRESS.

APPLICATION FILED .TLAN. 29, 1902.

N0 MODEL. 2 SHEETS-SHEET 1.

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INVENTOR:

5 2 Wi-kw WITNESSES:

No. 760,921. PATENTED MAY 24, 1904.

J. J. RIGBY.

DRAWING PRESS.

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UNITED STATES v Patented May 24, 1904.

PATENT OEEIcE.

JOHN J. RFGBY, OF BROOKLYN, NEW YORK, ASSIGNOR TO E. W. BLISS COMPANY,OF BROOKLYN, NEW YORK, A CORPORATION OF WEST VIRGINIA.

DRAWING-PRESS.

SPECIFICATION forming part of Letters Patent No. 760,921, dated May 24,1904.

Application filed January 29, 1902. Serial No. 91,731. (No model.)

To all whom, it may concern:

Be it known that I, JOHN J. RIGBY, a citizen of the United States,residing in the borough of Brooklyn, county of Kings, city and State ofNew York, have invented certain new and useful Improvements inDrawing-Presses, of which the following is a specification.

This invention relates to presses for drawing sheet metal into cup form.In such presses it is customary to stamp out a disk or blank of suitableshape from a sheet of metal, as tinned iron or steel, and by grippingthe edge or marginal portion between an annular die and blank-holderwith a graduated pressure to force down the central portion by means ofaplunger or punch, thereby forcing the metal into dished or cupped formwhile drawing its marginal portion out from between the blank holding orgripping dies. For forming any but shallow cups it is necessary torepeat this operation two or more times by successively-acting dies,drawing the blank each time to a smaller diameter and to a greaterdepth. This drawing operation has the efiect of stiffening the metal,rendering it brittle and liable to crack, so that afteracertain numberof drawing operations it is necessary to anneal the metal before it canbe further drawn. Such annealing is admissible with certain metalsasgold, silver, copper, and

brass-or with iron or steel if not coated or tinned; but it is notpossible with so-called tin or tinned iron or steel-plate, be-

cause the annealing requires a temperature so high as to fuse off thecoating of tin. For this reason in drawing cups from tinned plate suchdepth as can be produced ordinarily by of practicability, and allefforts to draw cups beyond a certain depth have failed. The extremedepth heretofore attainable cannot be exactly stated; but the limit ofpracticable depth has rarely exceeded two-thirds the diameter of thecup. In most arts wherein such sibility heretofore of drawing such deepcups or cans it has been necessary to construct them with seamed jointsof a body consisting of a sheet of tin bent into tubular form, with itsedges united by a side seam to form a tube and a bottom stamped out of asheet of tin and seamed to the lower end of such tube, these seams beingsoldered wherever the can is to contain liquids. Such seamed cans arenecessarily produced by a complicated series of operations, requiringseveral machines and much handling, so that the product is expensive,and they have the disadvantage of presenting an unsightly seam along oneside and a seam around the bottom. The desirability of producingseamless cans by a drawing operation has long been obvious.

My present invention provides dies for a drawing-press whereby it isrendered feasible to draw the cups or cans toa much greater depth thanheretofore and to such depth as to serve many of the purposes for whichseamed cans have heretofore had to be supplied.

' My invention is also applicable with advantage for drawing cups orcans of other metal than tinned iron or steel.

The nature and novel features of my invention will be made apparent inthe course of the following description.

Figure 1 of the accompanying drawings is a section of a sheet or plateof metal from which the blank is to be struck out. Fig. 2 is a sectionthereof, showing the usual first operation of stamping out the blank ordisk. Fig. 3 is a diametrical section of the blank after undergoing thefirstdrawing operationas heretofore practiced. Fig. 4 is a similarsection after undergoing the second drawing opera- .tion, and Fig. 5 isa similar section of the product of the third drawing operation. Fig. 6is a diametrical section of the dies constructed according to myinvention adapted for receiving the blank shown in Fig. 3 and drawing itinto that shown in Fig. 4:. Fig. 7 is a similar section of diesconstructed according to my invention for receiving the blank shown inFig. 4 and drawing it into that shown in Fig. 5. Fig. 8 is an ideal orexaggerated section illustrating the drawing operation, showing theactive elements of the dies, and showing the sheet metal being operatedupon. Fig. 9 is a similar section showing a modified arrangement ofdies. Figs. 10 and 11 are similar sections showing other modifiedarrangements. I

In the ordinary drawing operation a sheet or plate of suitable metal, astin, (tinned iron or steel,) a, Fig. 1, is placed in a combined stampingand drawing press, whereby at one stroke a blank, usually a circulardisk, is cut out from the sheet, as shown at Z) in Fig. 2, and thisblank is then drawn into a shallow cup, as shown at 6 in Fig. 3. If itis required to be of no greater depth, its bottom may be made square orwith a slightly-rounded corner; but if it is to be subjected toa furtherdrawing operation it is customary to form it with a conical portion 0between the sides and bottom. At the next drawing operation this blankI) is put in a press having blank-holding dies which engage the conicalportion 0, while a plunger or punch descends through such blank-holderand forces down the bottom of the blank, drawing the side portionsthereof through the conical space between the blank-holding surfaces,and thereby reducing the blank to a cup of substantially the proportionsshown in Fig. 4, the cup being of smaller diameter and of greater depththan the previous blank. In Fig. 4 I have shown the blank 5 as having aconical portion 0 between its sides and bottom. It will be understoodthat in ordinary drawing the product of the last drawing operation has asubstantially square or slightly-rounded corner or any other shape thatmay be desired within the limits of practicability and that ordinarilyonly the intermediate or preceding blanks have the conical portion corc. Heretofore in drawing tin a cup of substantially the depth of thatshown in Fig. 4 represents about the extreme of practicability. By myinvention, however, I enable much deeper cups to be made such, forexample, as that shown in Fig. 5, where the cup or finished product ofthe drawing operation is designated at I)". r

In an ordinary drawing-press the blank is gripped between annularblank-holding surfaces, which for the first operation are flat and forthe succeeding operations are ordinarily conical for fitting the cones 0or 0. Ordinarily the lower blank-holding surface is formed on a ring ordie, which ordinarily is supported on the bed of the press, while theupper blank-holding surface is formed on a blankholder, which ordinarilyis movable vertically, being carried upon the movable head or platen ofthe press. Essentially either the blank-holding die or the blank-holdermay be movable the one toward and from the other, or both may bemovable. It is practically necessary that means he provided for pressingthem together adJustably to grip the blank with a graduated pressure, soas to hold it just firmly enough to permit it to be drawn throughbetween them, their pinch upon the blank being not so great as to tearor break the sheet metal nor so slight as to permit the sheet metal towrinkle or corrugate while being drawn through between them.

In the ordinary drawing operation the middle portion of the blank isforced down by the male die or plunger (commonly called the punchthrough an annular female die, (commonly called the reducing-die) whichis formed ordinarily on its upper side with the blank-holding surface,and on its inner face it conforms to the plunger and approaches it soclosely as to allow room between them only for the thickness of themetal being drawn, so that the drawing operation carries the metal intoa diameter determined interiorly by the plunger and exteriorly by thereducing-die. Ordinarily the intervening space is of a thickness closelyapproximating that of the sheet metal being operated on, so that as theblank tends to thicken or corrugate by being drawn from a larger to asmaller circumference it is elongated sufficiently to preserveapproximately its original or normal thickness.

The usual cutting and drawing dies which perform the operationsindicated in Figs. 2 and 3 being well understood, I illustrate only thedies used for drawing the blank to the forms shown, respectively, inFigs. 4 and 5. Referring to Figs. (Sand 7 and also in part to Figs. 8and 9, let A designate the bed or fixed die-support of the press and letB designate a portion of the movable head or platen thereof, while Cdesignates the vertically-reciprocating spindle carrying the male die orplunger. It is well understood that in drawing-presses the bed A isstationary, the head B has a limited movement sufficient to bring theblank-holding surfaces together, and the spindle G has a greatervertical movement sufiicient to carry the plunger down through the dies.These parts being Well understood require no special illustration. Onthe bed A is mounted the usual die-block D, in which is carried anannular die E, resembling the ordinary blank holding and reducing die.In the same block and lower down is placed a secondary die F, which Icall the burnishing-die. Beneath the latter is the usual stripper-ringG, which is a split ring pressed inwardly by springs d, so that when theblank is forced down through it it contracts and hugs the plunger justabove the blank, so that on the upstroke of the plunger the blank isstripped off therefrom and caused to drop through the central opening ain the bed.

H is the plunger or punch, having its exterior conformed to the interiorof the blank or cup to be drawn and carried in the usual manner on thespindle G.

I is the blank-holder, carried, as usual, by

the headB and having its lower end formed with a blank-holding surface,which in these perceptible in Figs. 6 and 7. Instead of drawing theblank at once tothe requisite thinness this die is large enough on itsinner face to leave the metal of a somewhat greater thickness than itshould have in the finished product, and the metal is subsequentlyreduced by the secondary die F, which I call the burnishing-die, and theinner faceof which has a very slightly smaller diameter than that of thereducing-die E. The diiference between these two dies is shown to agreatly exaggerated scale in Fig. 8. In operation the blank as it isdrawn from the larger diameter 10 to the smaller diameter 11 isthickened, notwithstanding the elongating action of the dies, thisthickening at 11 being much exaggerated in Fig. 8. Subsequently as theblank is drawn through the die F, which more closely approaches theplunger, the metal is reduced in thickness, as indicated, so that theportion 12 is brought down to the required gage, which ordinarily willbe the same as that of the original metal sheet a. The burnishing-die Fis mounted loosely in a cavity in the block D, this looseness beingshown to a somewhat exaggerated extent in Figs. 6 and 7, a free spacebeing left above and surrounding the die F, so that it is capable ofslight vertical and horizontal movements. The die F is made ofcomparatively thin metal, which I believe in practice permits it to dishor bend slightly as the heavy pressure of the punch is received by it,this movement being permitted by the free space above the die. Theeffect of this is apparently to relieve the blank of a portion of thestrain upon it, perhaps by a slight increase in the working diameter ofthe opening of the die, although I am unable to state positively thatthis is the fact. I find, however, that it is practically essential thatthe die be made of comparatively thin metal and that it be unconfinedupon its upper face either by a retaining-wall or by the upper die. Inthe construction shown I provide a heavy wall or flange J, which servesto rigidly support the die E, so that the heavy pressure which isbrought to bear upon this die shall not be transmitted to theburnishing-die. The latter, as before stated, is so mounted in itscavity that it is also capable of a slight horizontal movement therein.This free horizontal play has the effect of enabling the die F to centeritself so as to embrace the-plunger with uniform pressure on all sides,so that with homogeneous metal it automatically assumes a positionexactly concentric with that of' the 7 plunger, while in the event of aslight inequality in the metal of the blank this die is enabled to shiftits position so as to compensate therefor and distribute the pressure orresistance equally around its entire circumference.

Practical experience with dies constructed according to my invention, asthus described,

has demonstrated that cups or integral cans may be successfully drawn ofa height or diameter, but also brings it down to the required thinnessoftwo dies separated by a suitable interval, whereof the first, which Icall the reducing-die, serves merely to reduce the diameter of the blankwithout attempting to bring the metal to the requisite thinness, whereasthe second, which I call the burnishing-die, has the sole function ofdiminishing the thickness of the metal. The remarkable result attainedby my invention may be due to some extent to an annealing or partialannealing effect, since the friction and molecular disturbance due tothe reducing and burnishing of the blank heats it to such extent thatwhen it drops out beneath the pressthe blank is much too hot forhandling.

It is found to be practically essential that the reducing and burnishingdies shall act upon the blank in rapid succession and during oneoperation of the drawing-press. It has been attempted to reduce theblank by one operation by forcing it through a die like the die E andafterward in another press or by a separate operation to reduce thethickness of the blank by forcing it through a burnishing-die like thedie F; but this has resulted in the cracking of the metal of the blanklongitudinally after the reducing and before the burnishing operation,owing apparently to the release of the metal from strain or, perhaps, topermitting it to cool before forcing it through the burnishing-die. Onthe other hand, it has been attempted and is the customary practice indrawing tin to make the one die perform the functions of my reducing-dieE and burnishing-die F by forming its inner face to so .closely conformto the plunger as to at once reduce the metal to the final gage. Thisoperates successfully with short or shallow blanks; but in attempting todraw deeper cups or cans than those heretofore successfully produced itis found that the blank almost invariably breaks either close to thebottom or around the side and tion not only reduces the blank to asmaller K IIO approximately parallel to the bottom, so that the metalfrequently parts before being drawn through the die, or if it issuccessfully drawn through is commonly found to be cracked or ruptured,so as to render it worthless. In my invention by separating thesefunctions and performing them by dies spaced somewhat apart the strainupon the metal, which with a single die would break it, is distributedso that the descending punch first draws the blank down through thelarger die E and after having partially drawn out the blank thencommences to force it through the smaller die F. Thus the shock orinitial blow is diminished and distributed over two points in the strokeof the plunger, thereby reducing the liability to fracture at or nearthe bend where the bottom joins the sides of the blank, while toward thelower portion of the stroke, Where the blank offers the greaterresistance to reduction by reason of the tendency to thicken toward itsupper portion, this portion of the blank is relieved of. the strain offinal reduction of thickness until it is drawn down into the lower dieF. It has also been attempted to employ two successive rigidlymounteddies having their active faces spaced somewhat apart, so that the upperone shall reduce the blank to the desired diameter, and the lower oneshall then reduce it in thickness; but this has resulted with deep cupsin the rupturing of the metal. The mounting of the lower or burnishingdie loosely in the manner set forth herein has successfully solved theproblem of drawing such deep cups of tin-plate.

.The exact separation of the dies E and F cannot be definitely stated,as it would probably vary for blanks of different sizes or thickness.The proportions shown in Figs. 6 and 7 have operated successfully forproducing cups of two and one-half inches to three inches diameter andof a length or depth somewhat in excess of their diameter. I prefer toseparate the dies as widely as the stroke of the press will allow. For apress of long stroke a separation as great as that shown'in Fig. 9 wouldprobably be advantageous. In this figure the die F is located so lowdown that it engages the blank just before the upper margin thereof ispulled through the blank-holding surfaces. It is probably advantageousto hold the blank in the blank-holder or at least between the plungerand the inner margin of 5 5= the reducing-die E until it begins to enterwithin the die F, although this is not certainly necessary to success. Icontemplate adopting the relative spacing shown in Fig. 10, where theblank enters the die F after it has been reduced by the die E andpreferably just before its margin passes out from within the latter.With a smaller blanksuch, for example, that its top would come to thepoint 13 in this figurethe blank will have passed entirely out from thedie E before entering the die F. I believe it to be essential that theblank shall be held on theplunger so as to be subjected during the onestroke to the action of the respective dies in order that the blankwhile still heated from the reducing operation may be subjected to theaction of the burnishing-die.

My invention may by a further development be applied in connection witha greater number of dies than the two dies E and F. For example, I haveindicated in Fig. 11 the use of three dies, of which the upper one, E,is the reducing-die. a partial diminution in thickness of the metal,while the third, F throws it to the final thickness or gage. Asanexample of proportions that may be followed I would state that inpractice with dies E and F, as in Figs. 6, 7, and 8, I have made the dieE with an internal diameter of .006 inch larger than that of the die F.With the arrangement shown in Fig. ll the reducing-die E may be of thesame in- The next, F, accomplishes ternal diameter as before, while thesuccessive dies F F may each be, for example, .003 inch smaller, or inFig. 11 the die E may be of larger internal diameter than that shown inFigs. 6, 7 and 8, being, for example, just'suffieiently smaller toprevent the metal crimping or corrugating in drawing through it, inwhich case the die F may be about .006 inch smaller and the die F .006still smaller. These proportions are given only by way of example andnot as limiting me to anydefinite proportions.

Ordinarily the reducing-die E is fixedly mounted in the-block D,whilethe burnishingdie F is freely mounted as described, so as to be able toautomatically center itself or accommodate itself to varying thicknessesof metal being drawn. In some cases, however, it may be desirable tomake the reducing-die E also free or self-adjusting. This is shown to anexaggerated extent in Fig. 7. To thus mount the die E is practicallyadvantageous, although it has not the same degree of advantage as in thecase of the burnishing-die F.

What I claim is 1. In a press for drawing metal of low duetility, thecombination of a plunger, and an annular die, the latter mountedloosely, so as to be capable of independent vertical and horizontalmovements.

2. In a press for drawing metal of low duetility, the combination of aplunger, a reducing-die and a burnishing-die, the latter mountformed ofthin metal so as to be capable of slight distortion during the drawingoperation, with means for mounting said die having a space above thedie, whereby the latter is unconfined upon its upper face, so as topermit such distortion.

5. In a drawing-press, the combination of a plunger and an annular die,the latter being formed of thin metal so as to be capable of slightdistortion during the drawing operation, with means for mounting saiddie having a space above and surrounding said die, so as to permitvertical and horizontal movements of the latter.

6. In a drawing-press, the combination of a plunger, a reducing-die,aburnishing-die, and

JOHN J. RIGBY.

Witnesses:

OTTO J. BEYER, W. E. MURDOGK.

